Insulating produce made in situ, fibres or particles used in its composition and a method of manufacture

ABSTRACT

Fibres, particularly glass or rock wool fibres coated with a modified polyvinyl alcohol-based polymer and suitable for use as a base material to produce a surface coating on a backing by simultaneous spraying of the coated fibres mixed with water and a cross-linking agent. A method of producing the fibres to make them suitable to be sprayed in the manner described is also provided.

BACKGROUND OF THE INVENTION

1. Field of the Invention:

The current invention relates to the building sector and particularlythe surface coating sector, especially with regard to insulation usingproducts, particularly insulants, made in situ from sprayed mineralfibres or particles and binders.

2. Background of the Prior Art:

It is known from French Pat. No. 2 442 807 corresponding to EP No. 11572to insulate a backing by spraying onto it firstly an organic binderconsisting of a filmogenic agent in colloidal solution in a solvent andthen simultaneously on the one hand and through a first jet, some of thesame organic binder as previously in colloidal solution and on theother, through a second jet, a mixture of particles, especially mineralfibres, and a powdered agent, especially borax, to coagulate the organicbinder, and possibly pigments and fillers.

This technique is essentially used for the insulation of industrialpremises, and when more particularly ceilings are involved, by reason ofthe action of gravity on the sprayed-on products, heterogeneity isobserved in the thickness of the insulant obtained, migration of thebinder and of possible colouring pigments in the thickness and theircollection together on the surface, which results in the formation of acrust which is unpleasant to look at and also technically harmful,especially from the acoustic insulation and fire-resistance points ofview.

These drawbacks are at least partly due to the fact that the binder,being distributed independently of the particles, fibres in particular,does not reach them all and therfore is not only non-uniformlydistributed but is also unsatisfactorily retained by the said paticlesor fibres.

Attempts have been made to reduce the quantity of binder sprayed on inorder to reduce the risk of fire but in this case the mechanicalproperties of the resultant insulant are inadequate.

Further, the quantity of binder which is distributed with the particles,fibers in particular, depends on the settings made by the individual whodoes the projection.

These settings can be changed during the projection so that theprojection of binder can be greatly increased for example to reinforcethe adhesion on the backing, thus resulting in an increased risk offire.

Furthermore, the excessive multiplicity of products which have to beconveyed onto a building site, and the risk of the binder freezing inwater, constitute additional drawbacks.

SUMMARY OF THE INVENTION

The present invention sets out to provide a surface coating and inparticular an insulation which can be produced in situ by spraying, inwhich the aforesaid disadvantages of the prior art are overcome, andparticularly in which the distribution of the binder through thethickness of the surface coating and particularly through the insulantproduced is more homogeneous, resulting in better technicalcharacteristics in the said surface coating, for instance insulant, inwhich also the proportions of binder are well controlled to avoid therisk of fire.

In an interesting development of the invention, it is likewise possibleto resolve the problem of the multiplicity of products needed on abuilding site in such a way as no longer to have to spray on more thanjust water at the same time as the fibres or particles.

To this end, the invention proposes a glass or rock wool fibre,generally a particle, coated with a polyvinyl alcohol-based polymer filmhaving free hydrophilic functions which can be subsequently reactivatedby water to allow crosslinking of the polymer in the presence of asuitable cross-linking or coagulation agent.

Advantageously, these hydrophilic functions which can be reactivated arecarboxyl functions.

Advantageously, the polymer is not completely saponified.

In a preferred embodiment, the invention proposes producing a mixture ofsuch particles or fibres which are coated with the powdered coagulationagent, this mixture being obtained by shredding of caked particles andin particular dried fibre felt and formed at the outlet of the fibre orparticle production and coating unit, to form elementary lumps of thesaid particles or flakes of the said fibres to which the powder isadded.

By way of application, the invention likewise proposes a method ofproducing a surface coating, particularly an insulant, on a backing fromsuch coated fibres or particles, the method consisting essentially inspraying onto the backing simultaneously firstly particles of fibrescoated with their reactivatable polymer, and on the other, in solutionor in dispersion particularly in water, the coagulation agent.

By way of application, the invention proposes a second alternativemethod of producing a surface coating, particularly an insulant, on abacking from coated fibres or particles, the method essentiallyconsisting in spraying onto the backing simultaneously and firstly theparticles or fibres coated with their reactivable polymer, of which theelementary lumps or flakes are mixed with the powdered coagulationagent, and on the other in spraying water. Advantageously, thecoagulation agent is a borate or alumina sulphate.

The invention likewise proposes an apparatus for spraying particles orfibres and liquid onto a backing.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in greater detail with reference tohe attached drawings which represent:

In FIG. 1: a diagrammatic view of a fibre producing and coating unitaccording to the invention;

In FIG. 2: a diagrammatic longitudinal section through an appartus forspraying particles, particularly fibres, and a liquid onto a backing,and

In FIG. 3: a cross-section taken on the line I--I through the apparatusshown in FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention relates to particles in general, adapted to be sprayedonto a backing in order to produce thereon a surface coating, forexample an insulating surface coating, and it is applied moreparticularly to fibres, especially glass or rock wool fibres.

In the ensuing description, we will take as an example solely rock orglass wool fibres, but it is understood that other particles arelikewise involved such as, for instance, ceramic fibres, expanded balls,particularly glass balls, vermiculite, etc.

The invention involves preparing treated fibres which can be stored andthen used subsequently to make a surface coating on a backing byspraying them against the backing, the junction with the backing and thevarious fibres inter se being brought about by reason of the productsused for treating the fibres and preset on the fibres, which arereactivated and cross-linked by the addition of a limited number ofadditional constituents and in a particularly advantageous form ofembodiment due to the addition of water only. This treatment of thefibres consists essentially in surfacing them with a modified polymerbased on polyvinyl alcohol and offering capacity for adhesion to thefibres and capacity for subsequent reaction with the water.

Adhesion to the rock wool or glass fibres results from the presence inthe polymer chain of functions of the cationic carboxyl type.

Advantageously, this adhesion to the fibres can be improved and/orsupplemented by the addition of a surface active agent of the aminooxide, amino lauryl type, which favours wetting of the fibres, spreadingof the polymer solution and thus the production of a sheathing film overthe major part of the surface of the said fibres.

The capacity for reactivation by water likewise depends on functionspresent in the polymer chain. Carboxyl functions in addition to thosewhich may have been monopolised in order to ensure engagement on thefibres can hydrolyse rapidly.

This capacity of the polymer for being reactivated by water canadvantageously be reinforced by resorting to incompletely saponifiedpolyvinyl alcohol polymers. The saponification rate may thus be limitedto around 65 to 85% and preferably 74 to 80%.

Furthermore, it is important that this polymer deposited on the fibresnot be cross-linked, or at least not completely at the temperatureswhich it will have to withstand when it is deposited on the fibres, inorder to retain its capacity for being reactivated by water. Thus, if itis deposited on rock wool or glass fibres just prior to their beingdrawn out, it must be able to remain incompletely crosslinked andgenerally reactivatable with water, despite temperatures of around 100°to 150° C. which the said fibres must withstand in order to completetheir production cycle.

Furthermore, it is necessary that this polymer be capable of easydistribution, because once it has been brought into solution, it must beable to circulate through pumps and equipment designed to distribute itover the fibres. Thus, a viscosity of a 4 to 10% aqueous solution ofthis polymer at 20° C. of around 5 to 6 centipoises is appropriate.

This low viscosity favours the transformation of the fiber felt intoflakes and also the re-wetting of the fibers' polymeric sheaths justbefore the gel is formed, when the projection on the backing is done.

Of the polymers which exhibit these characteristics and which aretherefore suitable, an appropriate commercial product is identified by:"PVA KL 506 of Messrs. KURARAY CO. LTD, OSAKA".

The fibres which are the object of the invention are therefore treatedas explained hereinafter.

After the fibres have been drawn out, that is to say after they havebeen produced, for example in the case of glass fibres, after thefibring of the glass which arrives in a stream 1 through a centrifuge 2,heated and rotating, drawing through the flames of burners 3, possiblyaspersion by water, particularly via a first ring 4 of sprayers, thesaid fibres, in the zone in which their distribution is stillhomogeneous, are subjected to a second spraying process with an aqueoussolution of the sheathing polymer of the invention, from a second ring 5of sprays. Thus coated, the fibres are received on a receiving belt 6 ofa conveyor, through which a suction is exerted. The felt which is thusconstituted by the fibres as a whole is then transferred to an oven 7where it is dried.

Throughout all these operations which follow depositing of the polyvinylalcohol based polymer on the fibres, the excess water accompanying thesaid polymer is at least partly eliminated so that the fibres are drywhen they leave the oven. A part of the excess water which is noteliminated can be incorporated into the surface coating in gel form.

In a glass fibre production unit such as has been diagrammaticallydescribed hereinabove, weights of water identical to weights of producedfibres can be eliminated.

Thus, therefore, polyvinyl alcohol based polymer solutions in a quantityby weight identical to the weight of fibres to be treated will besprayed at the exit of the fibres from the production stage, thepercentage of polymer by weight in the solution being around 2 to 20%and preferably 4 to 10%.

These possibly compressed fibres may be stored thus and be brought outagain only when required for use to produce a surface coating, forexample an insulating coating, on a backing.

In an alternative method of producing fibres for the same use, the saidfibres, pretreated by the polyvinyl alcohol based polymer, are fixedwith an agent for cross-linking or coagulating the polymer, and of theborate type, in powdered form.

This cross-linking agent may be deposited on the felt of dried fibresand, possibly compressed, the felt may be stored thus or may beimmediately shredded into fibre flakes to facilitate spraying.

The cross-linking agent may likewise be added to the fibres only afteror during their transformation to flake form. The addition of powder tothe surface of the felt and then a supplementary addition to the flakesis likewise possible.

The preferred cross-linking agent is pentahydrated sodium borate in theform of a fine powder of less than 40 micrometers granulometry. Sodiumborate decahydrate may likewise be used.

Larger grain sizes may also be suitable, but it is then less easy forthem to penetrate to the heart of the fibres.

It is possible likewise to use other cross-linking agents adapted tobridge the polymer chains, for example alumina sulphate.

Flakes of fibres mixed with the cross-linking agent in powdered form,possibly compressed, can be stored in this way until they are requiredfor use.

To produce a surface coating on the backing, ceiling or the like, it isenvisaged simultaneously to spray onto the said backing:

firstly the treated fibres which are shredded into flakes whichaccording to circumstances are alone or may be mixed with thecoagulation agent;

second, water which, according to circumstances, contains in solutionthe coagulation agent if the fibres do not contain it, or is alone ifthe fibres already contain the coagulation agent.

Of course, there is a possible midway situation: in the event of onlypart of the powdered cross-linking agent being added to the fibres, thenecessary supplement of the said cross-linking agent is brought insolution in the water needed for spraying purposes.

Therefore, the fibres and the liquid are simultaneously sprayed onto thebacking which is to be covered. By reason of the capacity of the polymerwhich sheaths the fibres to become well wet, particularly thanks to thehydrophilic function, especially free carboxylic functions, the wetting,the cross-linking reaction with the borate or the like which forms anhomogeneous adhesive gel enclosing each fibre, occurs very rapidly. Thelow viscosity of the polymeric solution used favours the quick wettingbefore the gelification. The sheathing of each particular fibre bypolymer which is adapted to react facilitates the production of ahomogeneous surface coating having desirable and regular mechanicalproperties.

Advantageously, to facilitate and reinforce adhesion of the surfacecoating to the backing, it is recommended to previously treat thebacking by covering it with a coating of binder consisting of thepolymer used for covering each fibre, in solution in water. The polymercontent may be greater than in the fibre coating solution.

Whether only water has to be sprayed simultaneously with the fibres orin the other case in which the fibres are sprayed alone while thecross-linking agent is added simultaneously with the sprayed-on water,the mat of fibres obtained has properties which are improved in relationto the prior art fibre mats, these improved properties being dueessentially to the fact that the individual fibres have been treated andcontain over a substantial proportion of their surface a polymer whichis adapted to form an adhesive gel together with the cross-linkingagent. In contrast to what has happened in the prior art, this adhesivegel will therefore develop homogeneously through the mass of the matcovering the backing.

The tearing resistance characteristics of the mat which is produced inthis way on a backing are about 50% better than those measured in a matproduced by a prior art technique in which the fibres have not beenpreviously treated by the polyvinyl alcohol based polymer.

Furthermore, particularly in the case where only water has to be addedto the pretreated fibre mixed with borate or the like, the building siteoperations are simplified, the satisfactory proportions of the variousingredients used in formation of the adhesive gel being guaranteed bythe fibre being prepared in a specialised production unit; the risks ofthe binder freezing in winter are overcome.

Furthermore, fillers or colouring pigments which it is always possibleto add to the fibre, for example in mixture with borate or the like, orwith water, will be better distributed over the thickness of the matobtained and will no longer collect on the underside of the said mat dueto migration through gravity; they will be more satisfactorily fixed atthe level of each fibre.

By reason of this technique, the fine fibres adapted to produce goodthermal insulation but which by reason of the barrier which they offerto penetration of the binder were not widely used in the prior art, cannow be used without limitation.

A spraying machine may be employed as shown in FIGS. 2 and 3.

It comprises on the one hand fibre distribution means and on the otherliquid distribution means, the liquid being solely water in thepreferred embodiment of the invention.

The fibre distribution means comprises filling means such as a hopper 10into which the fibre is introduced in the form of flakes mixed with thepowdered cross-linking agent unless it has already been introduced insolution in the water sprayed on at the same time. This hopper is fittedwith a discharge 11 and then a dispenser 12 of the screw type.

The fibres entrained by the screw of the dispenser 12 then enter acompression chamber 13 from which they are extracted by the action ofone or a plurality of blades 14 mounted, for instance, on an extensionof the shaft 15 of the screw of the dispenser 12.

Under the chamber 13 and connecting therewith through the aperture 16 isa carding assembly generally designated 17.

In the embodiment shown in greater detail in FIG. 3, this assembly 17comprises two rotary cards 18 inside a housing 19, the said cards beingsufficiently close to the mass of fibres compressed in the chamber 13that their teeth can scrape the mass and detach fibrous particlestherefrom. The particles are then introduced into a honeycomb chamber20. This chamber comprises a stator 21 of generally cylindrical form inwhich revolves a rotor 22 provided with fins 23 defining cells 24. Thesealing-tightness of the cells is provided by tongues 25 of semi-rigidmaterial fixed around the edge of the fins 23.

A gaseous medium, generally air, in a stream emitted by a blower 26, isadmitted at the bottom of the stator 21 through the aperture 27.Ejection of the fibrous particles entrained by the stream of gaslikewise occurs at the base of the stator 21 through the aperture 28 ina duct 29 terminating at a spray nozzle 30. This nozzle 30 is framed byat least two liquid spray nozzles 31 and 32, particularly for sprayingwater alone when the borate or the like has been introduced in mixturewith the fibres. The nozzles 31 and 32 are supplied with liquid inreserve from a tank 33 by a pump 34.

The surface coating mat thus obtained from rock wool or glass fibres isnot very expensive to produce. It has improved mechanical resistanceover the mats of the prior art, its fire-preventive properties areimproved and its appearance is agreeable. The fibres used to produce it,sheathed by their polymer, are protected until they are used throughoutall the processes of shredding, carding, etc., which they undergo.Moreover, the insulation coating can be covered for example with paint.This coating is durable and without any detrimental effect on thebacking.

Borate fixes the pH at a value around 9, so that the risk of an acidattack of the metallic parts of the backing does not exist, and so thatthe risk of a basic attack of the glass fibers does not exist. Thisinsulation coating can be deposited without alteration on backings atroom temperature or high temperatures up to, for example, 200° C.

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, theinvention may be practiced otherwise than s specifically describedherein.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:
 1. Dry particulate material comprised of fibers ofglass or rock wool for insulation wherein the surface of substantiallyeach particle of said material is uniformly coated with a film of apolymer comprised of polyvinyl alcohol having free hydrophilic chemicalfunctions adapted for subsequent reactivation by water to allowcross-linking of the polymer in the presence of a suitable cross-linkingagent.
 2. Material of claim 1, wherein the hydrophilic functions of saidpolyvinyl alcohol-based polymer are carboxyl functions.
 3. Material ofclaim 1 wherein said polyvinyl alcohol is not completely saponified, therate of saponification being limited to a level of around 65 to 85%. 4.The material of claim 3, wherein said saponification level is around74-80%.
 5. Material of claim 1, wherein the polymer further comprises anamino oxide or amino lauryl surface active agent.
 6. Material of claim1, wherein the polymer film is formed by coating said particulatematerial with an aqueous solution of the polymer, the vicosity of thesolution being around 5 to 6 centipoises at 20° C. and the proportion ofpolymer to water being around 2 to 20%.
 7. Material of claim 1 whereinit is mixed with powdered coagulation agent, the mixture being obtainedby shredding of the dried fibre felt formed at the outlet of theproduction and polymer coating unit, or by reduction of dried particlecakes and formed at the outlet of the production and polymer coatingunit, to form flakes or elementary cakes of particles to which thepowder is added.